Dielectric ceramics

Abstract

A dielectric ceramic which has a composition represented by the following general formula (I) and having a substantially perovskite crystal structure: (Ba.sub.1-x Sr.sub.x) (Mg.sub.1-y-w Ni.sub.y Co.sub.w).sub.1-u (Ta.sub.1- Nb z ) u 0 p (I) wherein x, y, z, u, w and p satisfy one selected from the following conditions: x=0, w=0, z=0, 0.001≦y≦0.088, 0.66≦u<0.72, and p represents a number with which the charges of the cations of Ba, Mg, Ni and Ta are neutralized, whereby the entire composition is electrically neutralized; x=0, z=0, 0.001≦y≦0.40, 0.001≦w≦0.40, 0.61≦u≦0.72, 0.002≦y+w≦0.40 and p represents a number with which the charges of the cations of Ba, Mg, Ni, Co and Ta are neutralized, whereby the entire composition is electrically neutralized; x=0, w=0, 0.04≦y≦0.90, 0.10≦z<0.96, 0.61≦u≦0.72, and p represents a number with which the charges of the cations of Ba, Mg, Ni, Nb and Ta are neutralized, whereby the entire composition is electrically neutralized; and w=0, 0<x≦0.25, 0≦y≦0.5, 0≦z≦0.8, 0.61≦u≦0.72, and p represents a number with which the charges of the cations of Ba, Sr, Mg, Ni, Ta and Nb are neutralized, whereby the entire composition is electrically neutralized.

What is claimed is: 
     
       1. A dielectric ceramic consisting essentially of a composition represented by the general formula:   Ba{(Mg.sub.1-y Ni.sub.y).sub.1-u Ta.sub.u }O.sub.p     wherein 0.001≦y≦0.088, 0.66≦u<0.72, and 2.990≦p<3.080.   
     
     
       2. A ceramic according to claim 1, wherein 0.66≦u≦0.68. 
     
     
       3. A dielectric ceramic consisting essentially of a composition represented by the general formula:   Ba{(Mg.sub.1-y-w Ni.sub.y Co.sub.w).sub.1-u Ta.sub.u }O.sub.p     wherein 0.001≦y≦0.40, 0.001≦w≦0.40, 0.61≦u≦0.72, 0.002≦y+w≦0.40, and 2.915≦p≦3.136.   
     
     
       4. A ceramic according to claim 3, wherein 0.002≦y+w≦0.35. 
     
     
       5. A ceramic according to claim 3, wherein 0.66≦u≦0.68. 
     
     
       6. A dielectric ceramic consisting essentially of a composition represented by the general formula:   Ba(Mg.sub.1-y Ni.sub.y).sub.1-u (Ta.sub.1-z Nb.sub.z).sub.u O.sub.p     wherein 0.004≦y≦0.90, 0.10≦z≦0.96, 0.61≦u≦0.72, and 2.915≦p≦3.080.   
     
     
       7. A ceramic according to claim 6, wherein 0.66≦u≦0.68. 
     
     
       8. A dielectric ceramic consisting essentially of a composition represented by the general formula:   (Ba.sub.1-x Sr.sub.x)(Mg.sub.1-y Ni.sub.y).sub.1-u (Ta.sub.1-z Nb.sub.z).sub.u O.sub.p     wherein 0<x≦0.25, 0≦y≦0.5, 0≦z≦0.8, 0.61≦u≦0.72, and 2.915≦p≦3.080.